remove mirror workflow

.github/workflows/mirror.yml

@@ -1,32 +0,0 @@
-# Mirror changes to this repo to Anthophila/codeql-action
-# whenever a PR is merged into master.
-name: "Mirror to Anthophila/codeql-action"
-
-# TODO change to trigger when master branch pushed/PR-merged
-on:
-  push:
-    branches:
-      - master
-
-jobs:
-  mirror:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v1
-    - name: Mirror
-      run: |
-        # Only run if running on private repo
-        if [ "${{ github.event.repository.full_name }}" == "github/codeql-action" ]; then
-          # setup deploy key
-          mkdir -p ~/.ssh
-          echo "${{ secrets.DEPLOY_KEY }}" > ~/.ssh/id_rsa
-          chmod 600 ~/.ssh/id_rsa
-          # add public repo as remote and push to it
-          git checkout master
-          git remote add public git@github.com:Anthophila/codeql-action.git
-          git push public master
-        else
-          echo "This workflow should only run on github/codeql-action"
-        fi